Human embryonal carcinoma grown in athymic mice and in vitro.

Tissue from 19 human testis tumors was transplanted into athymic mice. One embryonal carcinoma, ECCS, grew rapidly, and this tumor was studied both as a xenograft and an in vitro culture of xenograft-derived tumor cells. Xenografts showed no evidence of differentiation. The embryonal carcinoma cells were heteroploid and showed alkaline phosphatase activity. When tumor cells from the xenografts were grown in vitro, the cells formed aggregates resembling embryoid bodies with epithelium-like cells in the periphery. Regularly, another population of mouse cells which showed several criteria of malignancy overgrew the culture and could be subcultured continuously. These abnormal cells may result from an in vivo or in vitro transformation of mouse stromal cells.